A number of mechanisms are known for fixturing wires during bending operations. The prior art includes hydraulic mechanisms for clamping wires within a bending machine. These mechanisms relied upon jaws that closed on the wires and held the wires fixed within the clamp. In these mechanisms, the jaws clamp the wire with a force that prevents the wire from rotating relative to the jaws. In applications that require a wire to be rotated, the known clamps themselves must be rotated to rotate a wire about its longitudinal axis. The jaws exert a force on the wires, and static friction between the jaws and the clamps holds the wires fixed as the clamping mechanism itself is rotated.
In wire bending machines, the desire is to make the clamping mechanism as narrow as possible so that the wire can be bent as close as possible to the clamp itself. The need therefore is to make the clamping mechanism and its supporting elements as narrow as possible. Further, since the entire mechanism including jaws must be rotated, the clamping mechanism must be designed as compactly as possible. Hydraulic systems are the preferred method of generating the mechanical advantage required by such clamps, while keeping the mechanism itself compact.
The known hydraulic clamping mechanisms have several undesirable limitations. First, the known mechanisms have seals that wear out over time and are difficult to replace. As discussed above, the jaws of the known hydraulic clamps must rotate to rotate a wire. The known mechanisms have seals that transmit hydraulic fluid from the stationary part of the mechanism to the rotating part of the mechanism. These seals are prone to mechanical wear. When the seals wear out, they must be replaced. Replacing the seals requires machine downtime and is complicated because the seals must be carefully installed. Contamination is a problem, both during replacement and during ordinary operation of the mechanisms. The known seals are subject to contamination with debris common in manufacturing facilities, including metallic particles, grit, oil, and other damaging foreign material.
Second, the known hydraulic clamping mechanisms have a limited range of motion. The same seals that transmit hydraulic fluid from the stationary part of the mechanism to the rotating part of the mechanism also limit the range of motion for the mechanisms. Known hydraulic clamping mechanisms are typically limited to approximately 250 degrees of rotation.
Third, the known hydraulic clamping mechanisms have hoses and other appendages that make them wider than is frequently desired. A mechanism that is narrower than the known mechanisms is desired, as this increases the flexibility of machines that incorporate such wire clamping mechanisms.